Ground prong for an electrical plug

ABSTRACT

A ground prong for an electrical plug of the type providing two current-carrying prongs and a ground prong for connection to a three-wire electrical system, the ground prong being provided with a plurality of spaced apart, radially outwardly extending ridges along its length to make a better ground connection with the conventional ground contact in a three-prong electrical wall receptacle.

United States Patent 1191 Ezzo 339/196 R Garrett 1 Jan. 7, 1975 [5 1GROUND PRONG FOR AN ELECTRICAL 2,248,082 7/1941 Herman .3 .1 339/195 R L2,861,324 11/1958 Klumpp t 3.39/14 P 2,873,988 2/1959 Bartholomew....339/95 R Inventor: Lewis Garrett, I020 7 3,013,242 12/1961 Terlinde33,9/14 RP Hialeah, Fla. 33012 3.644.869 2/1972 Newman 339/19 [22]Filed: Nov. 21,1973 I Primary bxammer-Roy D. Frazier 1 1 PPbio-1.4181074 Assistant Examiner-Robert A. Hafer -[52] US. Cl 339/14 P,339/95 R [57] ABSTRACT [51] Int. Cl HOlr 3/06 A ground prong for anelectrical plug of the type pro- [58] Field of Search... 339/14, 95,252, 278, 256 C, I Viding two currem carrying prongs and a ground339/258 196 prong for connection toa three-wire electrical system, 1 theground prong being provided with a plurality of [56] References C'tedspaced apart, radially outwardly extending ridges UNITED STATES PATENTSalong its length to make a better ground connection 1.627,442 5/1927Luthy..... 339/95 B with the conventional ground contactin a three-prong1.650.546 11/1927 Strahan .1 339/258 C electrical wall receptacle.1.671.226 5/1928 2.049.560 8/1936 6 Claims, 4 Drawing Figures 1 GROUNDPRONG FOR AN ELECTRICAL PLUG STATE OF THE PRIOR ART Conventionalthree-prong electrical plugs of the type commonly connected to athree-wire electrical system are comprised of two current-carryingprongs and a ground prong. The ground prong is generally round orhorseshoe shaped in vertical, transverse cross section and provides asmooth outer surface for contact with an internal contact member in athreeprong wall receptacle.

Three-wire electrical systems are generally provided for electricaldevices such as household appliances and power tools which come incontact with human being while in operation. The safety factor of suchthree-wire electrical systems is dependent entirely on the groundconnection between the ground prong on the plug and the internal groundcontact in the female wall receptacle.

BACKGROUND OF THE PRESENT INVENTION The present invention pertains to aground prong for an electrical plug of the type. commonly connected to athree-wire electrical system by a cable extending therebetween.Electrical plugs of this type provide a pair of current-carrying prongsand a ground prong for reception in a conventional three-prong wallreceptacle or in a three-prong adaptor plug which provides receptaclemeans in one end for the three prongs and two current-carrying prongs,extending outwardly from the opposed end, for reception in aconventional twoprong wall receptacle. Adaptor plugs of this natureinclude a wire connection, commonly called a pigtail, between theinternal ground contact and a wall box, containing the receptacle. Thepigtail generally provides a forked end for reception between a screwand a cover plate over the wall box, the screw forming a groundconnection to said wall box.

The effectiveness of the ground connection between the ground prong onthe plug and the ground contact in the wall receptacle or adaptor plugis entirely dependent on the nature of the contact therebetween. Becauseof the considerable periods of time that often elapse between the usageof many household applicances and hand-operated power tools, aconsiderable degree of oxidation forms on the surfaces of both theground prong, carried by the plug, and the ground contact in the wallreceptacle. As a result, a poor electrical circuit is formedtherebetween.

To obviate this condition, the ground prong of the present invention isprovided with a plurality of spaced apart, radially outwardly extendingridges along its length to provide a better electrical ground connectionbetween said prong and the receptacle ground contact. The apex of eachridge provides a scraping action along the length of the receptaclecontacts every time the plug is inserted into or withdrawn from thereceptacle which removes the oxidation from the surfaces of bothelements.

The internal ground contact means of most conventional three-prong wallreceptacles or adaptors genen ally comprises one or more copper springleaves which flex radially outwardly when the plug is inserted therein.

To further enhanace the degree of contact between the ground plug andthe receptacle ground contact, the

ground plug of the present invention may be provided with a plurality oflongitudinal slits, substantially along its length, to form a pluralityof somewhat flexible segments which conform with the internal,flexible'receptacle contacts to insure a ground contact, therebetween,along their respective lengths.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of athree-prong electrical plug including a ground prong in accordance withthe present invention;

FIG. 2 is an enlarged, fragmentary, side elevational view of the groundprong of FIG. 1, extending outwardly from the plug;

FIG. 3 is a cross sectional view, taken along the line 3-3 of FIG. 2;and

FIG. 4 is a cross sectional view similar to FIG. 3, illustrating amodified form thereof.

DETAILED DESCRIPTION OF THE DRAWINGS With reference to the drawings: inwhich like reference characters designate like or corresponding elementsthroughout the various views and with particular reference to FIG. 1, athree-prong electrical plug, designated generally as 10, is illustratedwith a pair of current-carrying prongs l2 and 14 and a ground prong 16,extending outwardly from a first end thereof. The plug 10 includes aninsulating main body portion 18 and a conduit 20, extending outwardlyfrom a second end enclosing two current-carrying wires 22 and 24connecting with the prongs l2 and 14, and a ground wire 26 connectingwith the ground plug 16. The various prongs l2, l4 and 16, and theconduit 20 include end portions molded into the main body portion 18 ina conventional manner with the various wires 22, 24 and 26 beingconnected with the respective prongs 12, 14 and 16 therein.

As best illustrated in FIGS. 1 and 2, the ground prong 16 is preferablyof a thin walled tubular configuration being longitudinally slotted,substantially along its length, as at 30, 32, 34 and 36 to form fouroutwardly extending segments 38, 40, 42 and 44. Each segment is providedwith radially outwardly extending ridges, designated generally at 45. Inone preferred form, illustrated in FIGS. 1, 2 and 3, the segments 38,40, 42 and 44 form a generally tubular transverse configuration, theridges 46 and 48 on the bottom and top segments 40 and 44 being formedgenerally in a parallel, transverse disposition and the ridges 50 and 52on the respective, .opposed side segments 38 and 42 being formed in anangular relationship with the slots 30, 32, 34 and 36. The dispositionof the ridges as above described are by way of example only and are notintended as a limitation of the present invention.

FIG. 4 illustrates a modified form of the present invention in which theground prong 16' is generally horseshoe shaped in cross sectionalconfiguration. In this form, ridges 44' are radially, outwardly formedfrom the outer surface thereof in a spaced apart, parallel transversedisposition or in an angular relationship to the respective edges 54 and56 thereof. The prong l6' may be longitudinally slotted to form two ormore segments, the ridges 44' may also be provided in any combination oftransverse and/or angular dispositions on the respective segments.

What is claimed is:

1. An electrical plug including an insulating main body portion having afirst end with a pair of currentcarrying prongs and the ground prong,extending outwardly therefrom, for reception in a conventionalthree-prong receptacle and a second end having a three-wire conduitextending outwardly therefrom, the prongs and conduit including innerend portions, fixed relative to the main insulating body portion thereofwith the three wires being connected therein with the respective prongs,said ground prong comprising an elongated member having an outer surfacewith a plurality of spaced apart, outwardly extending ridges thereon,said ground prong being of a generally thin walled tubular configurationand longitudinally slotted substantially along its exposed length, todefine a resilient prong, said prong being provided with said ridgeswhich extend generally radially outwardly therefrom, said resiliencyallowing said ground prong to compress radially as it engages a socket,substantially along the exposed length thereof.

2. The ground prong as defined in claim 1 wherein said inner endportions are molded in said main insulating body portion.

3. The ground prong as defined in claim 1 wherein said ground prong isslotted to define four generally equal sized prong segments.

4. The ground prong as defined in claim 3 wherein a first opposed pairof said prong segments provide ridges in a spaced apart, generallyparallel, transverse disposition and a second opposed pair of said prongsegments provide ridges in an angular relation to said slots.

5. The ground prong as defined in claim 1 wherein said prong is of agenerally horseshoe, transverse configuration.

6. The ground prong as defined in claim I wherein said prong islongitudinally slotted, substantially along its exposed length, todefine a plurality of extending prong segments.

1. An electrical plug including an insulating main body portion having afirst end with a pair of current-carrying prongs and the ground prong,extending outwardly therefrom, for reception in a conventionalthree-prong receptacle and a second end having a three-wire conduitextending outwardly therefrom, the prongs and conduit including innerend portions, fixed relative to the main insulating body portion thereofwith the three wires being connected therein with the respective prongs,said ground prong comprising an elongated member having an outer surfacewith a plurality of spaced apart, outwardly extending ridges thereoN,said ground prong being of a generally thin walled tubular configurationand longitudinally slotted substantially along its exposed length, todefine a resilient prong, said prong being provided with said ridgeswhich extend generally radially outwardly therefrom, said resiliencyallowing said ground prong to compress radially as it engages a socket,substantially along the exposed length thereof.
 2. The ground prong asdefined in claim 1 wherein said inner end portions are molded in saidmain insulating body portion.
 3. The ground prong as defined in claim 1wherein said ground prong is slotted to define four generally equalsized prong segments.
 4. The ground prong as defined in claim 3 whereina first opposed pair of said prong segments provide ridges in a spacedapart, generally parallel, transverse disposition and a second opposedpair of said prong segments provide ridges in an angular relation tosaid slots.
 5. The ground prong as defined in claim 1 wherein said prongis of a generally horseshoe, transverse configuration.
 6. The groundprong as defined in claim 1 wherein said prong is longitudinallyslotted, substantially along its exposed length, to define a pluralityof extending prong segments.